New Guidelines Help Highway Agencies Make the Most of Maintenance

Motorists rank pavement conditions as the top priority improvement needed on the Nation's highway system, according to a recent survey. They're tired of rough roads, damaged suspensions and tires, and maintenance-caused traffic delays. Highway agencies, meanwhile, are spending one-fourth of their budgets on pavement maintenance and repairs. The Strategic Highway Research Program (SHRP) assessment project found that SHRP's guidelines on materials and methods for repairing and maintaining asphalt and portland cement concrete pavements can help highway agencies provide better pavement conditions and make the most of their maintenance budgets.

Under SHRP, researchers developed guidelines on how to select the best materials to use when repairing common problems, such as potholes and cracks. SHRP also produced guidelines on how to select the most appropriate preventive maintenance treatments and how to use those treatments in a comprehensive preventive maintenance strategy.

In its analysis, the Texas Transportation Institute (TTI) focused on the economic benefits to be gained from using SHRP's guidelines on pothole patching techniques and preventive maintenance strategies. The other products of SHRP's pavement maintenance research have not yet been used extensively enough to allow benefits-versus-cost comparisons.

Pothole Patching

State highway agencies spend $300 million to $400 million per year to fix potholes. TTI estimated that local highway agencies, which maintain most of the roads in this country, spend about twice that much.

In most cases, highway agencies patch potholes using locally available cold-mix materials applied with the semi-permanent method or the throw-and-roll method. SHRP found that it is the quality of the materials rather than the repair method used that has the biggest effect on the quality of the pothole patch: the throw-and-roll method with quality patching materials can produce repairs that last as long as the semi-permanent method.

In its analysis, TTI assumed that highway agencies that switched to high-quality materials applied with the throw-and-roll method or the extremely quick spray-injection method could cut repair costs by 25 percent. The result_highway agencies could save as much as $89 million per year.

Preventive Maintenance

To analyze the economic benefits of preventive maintenance, TTI assumed that, on the average, pavements receive a preventive maintenance treatment after 10 years of life, then have an expensive overlay applied at 15 years. The research institute assumed that, by following SHRP's recommendations, highway agencies would apply an appropriate preventive maintenance treatment at 7 years in the pavement's life and again at 14 years; this would likely delay the need for a costly overlay until the pavement has been in service for 19 years. The total savings could reach $384 million per year.

Improved preventive maintenance strategies will also save motorists money. Because roads will be in better condition, drivers won't have to slow down for rough pavement and vehicles will suffer less damage, thus saving between $167 million and $627 million per year, depending on how quickly highway agencies implement the SHRP guidelines.

Case Studies

Case studies collected to date substantiate these predictions.

The Alaska Department of Transportation's Glennallen District decided several years ago that it could no longer accept poorly performing, expensive cold mix materials for pothole repairs. The district decided to switch to a patching material custom-made for conditions in the area. The custom mix is performing extremely well_pothole repairs now last two to four times as long as they used to. In addition, the new material can be stored for extended periods of time, allowing the district, which is located in a remote area, to buy materials in bulk.

Another highly recommended pothole repair technique, the spray-injection method, is paying off for the Larimer County (Colorado) Road and Bridge Department. "There is absolutely no comparison between the spray-injection method and conventional pothole patching methods," says crew leader Ken Mosness. "Not only is the machine faster and easier to use, but the finished work is also very durable and longer lasting."

TTI predicts that highway agencies will get their money's worth from SHRP research on pavement repairs and preventive maintenance. TTI estimates that research, development, and implementation costs for the SHRP pavement maintenance products will total $45 million over 20 years but that's just a fraction of the potential annual savings.

The Strategic Highway Research Program looked at three methods of repairing potholes.

The throw-and-roll method, in which the crew simply fills the pothole with patching material, then compacts the patch by driving over it.

The semi-permanent method, which involves squaring up the edges of the pothole with a saw or other equipment, placing the repair material, and compacting it with a small vibratory compactor. The technique is effective but very labor-intensive.

The spray-injection method, which employs special truck- or trailer-mounted equipment that shoots asphalt and aggregate into the pothole. Although the spray-injection equipment is expensive, the technique is extremely fast and can be done by a crew of just one or two workers.

Later this year, the Federal Highway Administration (FHWA) will update its manuals of practice on preventive maintenance techniques. These manuals will build on guidelines developed under SHRP. FHWA will also begin holding regional showcase workshops that expand on the SHRP workshops on innovative repair materials and preventive maintenance treatments, which were held regionally over the past 2 years. The participants' workbooks for those workshops are available from FHWA.

For more information on innovative repair materials or to request a copy of the workshop workbook, contact Joe Huerta at FHWA (phone: 202-366-1556; fax: 202-366-9981; email: joseph.huerta@fhwa.dot.gov). For information on preventive maintenance treatments or to order the workshop workbook, contact Angel Correa at FWHA (phone: 202-366-0224; fax: 202-366-9981; email: angel.correa@fhwa.dot.gov).

In addition, SHRP publications are available from the Transportation Research Board; check the TRB Web site at http://www2.nas.edu/trbbooks/SHRP1.html.

More detailed information on the benefits-versus-costs analysis of the SHRP products, as well as more than 100 case studies of how highway agencies are using those products, are available at the RoadSavers home page.